mardi 2 septembre 2008

Aquila 3

AlshainBeta Aquilae

Distance (Light Years)44.7 ± 0.5Visual Magnitude3.71Color (B-V)0.86Names For This StarAccording to Allen, "Alshain" is derived from Persian name for Aquila, Shahin tara zed, "The Star-Striking Falcon." An alternative spelling is "Alschairn."Description of the StarAlshain is a binary star system. Alshain A is a yellow G8IV subgiant star about 5 times as luminous as the sun.Alshain B is a red M3 dwarf. This star appears to be of 12th magnitude. From the spectral type, the star would have 40% of the diameter of the sun and an effective temperature of 3100 K. The dwarf would have about 1.5% of the luminosity of the sun and 30% of the sun's mass. (An apparent magnitude of 12 would imply 0.2% of the sun's luminosity.)The observed separation of 13 seconds of arc between the components would correspond to a projected distance 180 AU, that is, about 4.5 times the radius of the solar system out to Pluto.

Altair

Alpha Aquilae

Distance (Light Years)16.77 ± 0.08Visual Magnitude0.76Color (B-V)0.22Names For This StarThe name Altair is derived from the Arabic name for the constellation of Aquila: Al Nasr al Tair. An alternative spelling for the star name is "Atair."Description of the StarAltair is a white A7V main sequence star. The star is about 1.6 times the diameter of the sun.The spectral type implies an effective temperature of 8100 K, a luminosity about 9 times that of the sun, and a mass almost twice that of the sun.According to Burnham Altair is one of the most rapidly rotating stars known. The rotational speed at the equator, as determined from the spectrum, amounts to 160 km/s, which implies a rotational period of about 6.5 hours. (The equatorial rotation period of the sun is 25.4 days.) This very rapid rotation suggests that the star is very appreciably flattened by centrifugal force, so that the polar diameter might be one half of the diameter measured across the equator.

TarazedGamma Aquilae

Distance (Light Years)461 ± 49Visual Magnitude2.72Color (B-V)1.52Names For This StarThe name of this star, Tarazed, comes from the Persian name for the constellation of Aquila, Shahin tara zed, "The Star-striking Falcon."The The Bright Star Catalog also gives the name Reda for this star.Description of the StarTarazed is an orange K3II bright giant having about 1400 times the luminosity of the sun.